A standard shower head is known having an adjustment ring that can be turned to vary the flow from the shower head. The ring can vary volume or even switch the shower head between different spray modes, for instance concentrating flow from a single central large-diameter port or from an array of peripheral small-diameter ports.
In German patent 3,047,336 filed 24 Jun. 1982 by G. Kottek such a system is shown having inlet ports from which flow can be directed to a central large-diameter massage port or to peripheral smaller-diameter shower ports. An axially displaceable piston in the shower head can move a seal past the inlet ports to divert the flow as desired, and can even move over the inlet ports to provide some flow control to the shower ports.
Such a system is fairly bulky, in particular in the axial direction. It is therefore not readily adaptable for use in a hand-type shower. Furthermore the adjustment only basically allows two modes of operation.